Cloned Mice from Frozen Bodies – Are Mammoths Next?

Clones from Frozen Mice – Potential to Resurrect the Mammoth

A team of Japanese scientists have succeeded in cloning mice whose bodies had been frozen for as long as sixteen years. It may be possible to further refine the techniques to clone the mice and develop ways of ensuring the survival of endangered animals today as well as possibly being able to bring extinct animals such as Woolly Mammoths back.

In a paper published in the scientific journal “the Proceedings of the National Academy of Sciences”, the Japanese scientists proved that animals could be cloned even though their cells had burst and showed other signs of damage.

The Japanese researchers led by Sayaka Wakayama of the Centre for Developmental Biology, Kobe made mice clones with a technique called nuclear transfer. This involves using the nuclei of egg cells, cells of animals that had been stored at -20 degrees Celsius and from animals first frozen in 1992. The egg cell nuclei is replaced with the nucleus of an ordinary cell from the animal due to be cloned. When done with the right chemical or electric trigger, the egg division process can be started as if it had been fertilised by sperm. Normally, cells that have been frozen tend to be damaged as the water in the cells expands rupturing membranes during the freezing/thawing process. Cells that are going to be used for cloning purposes are treated with special chemicals and additives called cryopreservation agents to help overcome any problems associated with the freezing process.

The team stated in their paper:

“Thus, nuclear transfer techniques could be used to ‘resurrect’ animals or maintain valuable genomic stocks from tissues frozen for prolonged periods without any cryopreservation”.

This raises the possibility of being able to use material from Siberian mammoths that perished thousands of years ago, but have been preserved in the frozen permafrost. Genetic material could be gathered and then a Woolly Mammoth clone produced.

Anticipating this line of enquiry, the Japanese researchers stated that:

“However, it has been suggested that the ‘resurrection’ of frozen extinct species (such as the Woolly Mammoth) is impracticable, as no live cells are available, and the genomic material that remains is inevitably degraded.”.

Producing clones from mice that had been kept frozen for many years is a remarkable achievement. The cells and the precious DNA that they contain would have been damaged and no cryoprotectants were applied to the mice before they were frozen. Ironically, the team tried to clone the mice using a variety of cells, but they discovered that in this experiment it was the brain cells that worked best. This is a bit of a mystery, as no one has yet cloned any living mouse from a brain cell.

Many animals have been cloned, starting with Dolly the sheep, cloned by British scientists in the 1990s (1996). Other cloned animals include pigs, cattle, mice and dogs. Livestock breeders want to use cloning to start elite herds of desirable animals, and doctors want to use cloning technology in human medicine, for example to produce organs from pigs that are suitable for use in human transplants.

There were a number of Mammoth type species. The Woolly Mammoth (M. primigenius) existed during the Pleistocene age (1.75 million years to approximately 10,000 years ago). They were about 3.7 metres long, 3 metres high at the shoulder and would have weighed around 3 tonnes (males bigger than females). Woolly Mammoths had sloping backs, dense fur, high single-domed heads, small ears (to cut down on heat loss), large, curved tusks and a short, stumpy tail.

An Illustration of a Woolly Mammoth

Picture Credit: Everything Dinosaur

Remains of mammoths are frequently found in Siberia, often in the spring during the winter thaw. A baby mammoth was found preserved this way in July 2007.

This baby mammoth was nicknamed Lyuba (after the wife of the reindeer herder who discovered the carcase). Further work is required before it can be demonstrated that nuclei can be collected from the cells of these ancient animals and made viable for generating offspring following a nuclear transfer process.

Commenting on the research carried out by the Japanese team, George E. Siedel Jr. of the Colorado State University in Fort Collins stated: “it’s not the first time that dead animals have been resurrected. Previously, they were stored much colder than these temperatures and they were generally treated in a special way [cryoprotectants]“.

A number of scientists have undertaken research into the potential cloning of mammoths, although there are no live cells available and the genetic material within the frozen and then thawed out cells is likely to be severely degraded.

Yet the creation of live animals from material taken from a mouse frozen for more than a decade and a half suggests that scientists may be able to use nuclear transfer techniques to clone extinct species or maintain stocks of genetic information without special preservation methods, the study concluded.

Reproduction of a Woolly Mammoth from remains frozen in ice isn’t expected to happen within the next decade, as the cells are likely to die once they are thawed out and there are no live eggs. However, some transfer cloning using another species as a “surrogate mother” may be possible with the Indian elephant being the most likely candidate.

Woolly Mammoths remain popular with prehistoric animal collectors and school children. Team members at Everything Dinosaur have recently helped in a project to introduce the theme of extinction events and climate change within the UK national teaching curriculum. The decline and extinction of the Mammoth was a central concept in the teaching plans. If the cloing programme proves ultimately successful we may have to re-write our teaching materials.